During a write to a receiving media by a transducer head, the transducer head uses a magnetic read sensor to read up-track of the writing location to assure the desired data track is targeted during the write operation. As media areal or bit density increases, maintaining a consistent track between the read sensor and a writing pole on the transducer head becomes increasingly difficult.
Additionally, in the continuing effort to increase areal density, media with arrays or patterned cells have been designed where each cell can hold a bit of data (bit patterned media (BPM)). On such BPM, data may be stored in individual cells along a data track defined by the patterned bits. However, each patterned bit is temporally synchronized with each data bit. Otherwise, data insertion may occur on an incorrect patterned bit or a patterned bit may be skipped for data writing. Therefore, one of the challenges with BPM is placing the head over the bit of interest accurately during writing. This is especially challenging due to the small size of the patterned bits (e.g. 1 nano-meter wide) and timing control requirements in a disc system rotating at high speeds (e.g. 20-50 pico-seconds per rotation). Other media forms exhibit similar challenges.